Impact of allelic variation in jasmonate repressors on proteoform structure, co-receptor assembly and plant performance
A master regulator of plant growth, defense, and fertility is the phytohormone jasmonate (JA-Ile) that triggers transcriptional changes necessary to promote plant fitness. During vegetative growth, JA-Ile levels are very low and JA-Ile responses are kept repressed by a modular repressor complex consisting of JASMONATE ZIM-DOMAIN (JAZ) repressors, the adaptor protein NOVEL INTERACTOR of JAZ (NINJA), and the general transcriptional co-repressors TOPLESS (TPL). However, JA-Ile levels rise rapidly in response to a stress stimulus and promote the binding between JAZs and the F-Box protein of an E3 ubiquitin ligase named CORONATINE INSENSITIVE 1 (COI1). This interaction leads to JAZs ubiquitylation and consequent degradation, liberating transcription factors (chiefly MYC2, MYC3 and MYC4) to initiate the transcription of JA-responsive genes. Although key components of JA-Ile perception and signaling have been identified, it remains unclear how can a single bioactive molecule regulate the large heterogeneity of physiological events observed for JA-Ile responses. By using the model plant Arabidopsis, the project aims to structurally and functionally characterize naturally occurring proteoforms of a key repressor of JA-Ile signalling. The project combines plant protein biochemistry with structural biology (mainly NMR spectroscopy) to uncover molecular details of underlying integration networks, and ultimately assess their impact on plant performance.